Forget the calculator, this book will teach you speed calculations in your mind or with a pencil. To count faster, it is enough to think a little differently, its author Yngve Vogt is sure - the Norwegian journalist of the scientific journal Apollon and a fan of mathematics. You will learn about simple and boring fast counting methods, which only require knowledge of basic arithmetic rules. The Trachtenberg method, the Chinese way of counting with dashes and many other mathematical techniques will help you easily add and subtract, multiply and divide, extract the square root and square large numbers. And you'll also find extraordinary facts and fascinating stories about numbers and the people who are crazy about them, and a brief thousand-year history of number systems, from ancient Greece to today's digital age.